Cutting Class(1989) [Colleen]: Killed (off-screen) by Donovan Leitch after he drags her away under the bleachers during a game. (Thanks to Verne)

The Outer Limits: Nest(2000) [Marcy Newhall]: Commits suicide by stabbing herself in the stomach, believing that she'd been infected by the insects; she dies (off-screen) in the infirmary shortly afterwards. (Thanks to Stephen)

The Barber (2001) [Sally]: Strangled (off-screen) by Malcolm McDowell in her bedroom. Her body is shown afterwards when the police investigate the scene, then again in the morgue.

Slither(2006) [Brenda Gutierrez]: Bursts apart while "giving birth" to a swarm of sluglike aliens, after having been transformed into their host/mother and swelling to immense proportions. (Thanks to Eric)